1. Field of the Invention
This invention relates to one-piece, stamped, sheet metal fasteners for receiving and engaging externally threaded fasteners of the type having external thread engaging members formed therein and in particular to one-piece, stamped, sheet metal fasteners having an arcuate leg in which the external thread engaging members are formed for threadably retaining and lockingly engaging an externally threaded fastener, the arcuate leg defining an arc having a radius and a chord, the ratio of said radius to said chord, in the non-deformed position of said arcuate leg, being in the range of 1:1.4 to 1:1.8 and preferably in the range of 1:1.5 to 1:1.7.
2. Description of Prior Art
Stamped, one-piece, sheet metal fasteners of the type having external thread engaging members formed therein are well known in the prior art. Examples of such stamped, sheet metal fasteners of the "U" type may be seen by reference to U.S. Pat. Nos. 2,062,685 and 2,101,287. Stamped, sheet metal fasteners of the type having an arcuate leg in which the external thread engaging members are formed may be seen by reference to U.S. Pat. No. 2,236,929. Stamped, sheet metal fasteners of the type seen in the above mentioned patents, and modifications thereof, have been highly successful and continue to enjoy wide usage today. However, such stamped sheet metal fasteners require a relatively large clamping load to achieve a locking engagement with the received externally threaded fastener sufficient to provide a vibration resistant joint for connection such as is required for automotive use and the like. Such a relatively large clamping load, or tensile force in the externally threaded fastener, is not desirable if the fastener is utilized in connection with relatively crushable and/or deformable panels, such as plastic panels, or the like. Such highly tensed externally threaded fasteners, when utilized with relatively brittle plastics such as lucite, tended to crack the brittle plastic, and when utilized with relatively soft plastics tended to cause migration of the soft plastic. In view of this drawback, stamped, sheet metal fasteners of the "U" type have not enjoyed wide acceptance in applications wherein a relatively large clamping force would be applied to a plastic panel, such as a plastic spacer plate, to achieve a vibration resistant connection.